“A note on the economic lot size of the integrated vendor–buyer inventory system derived without derivatives”: A comment

Wee and Chung [Wee, H.M., Chung, C.T., 2007. A note on the economic lot size of the integrated vendor–buyer inventory system derived without derivatives. European Journal of Operational Research 177, 1289–1293] use the complete squares method to locate the optimal solution of the integrated system’s total cost TC(Q, B, n). However, their algebra method has shortcomings such that it may be invalid. The main purpose of this paper is to overcome those shortcomings and present complete proofs for Wee and Chung (2007).